Semiconductor lasers that comprise a laser cavity defined by two parallel laser facets are known. Among these are Fabry-Perot lasers and distributed feedback (DFB) lasers.
Despite much effort aimed at improving the reliability of lasers with facets, such lasers frequently are subject to early performance degradation and/or laser failure. This problem is particularly severe in high power lasers, e.g, in lasers that would otherwise be well suited as pump lasers for optical fiber amplifiers in optical communication systems.
The above referred-to performance degradation or failure typically is connected with degradation of one or both laser facets. Facet degradation modes include catastrophic optical damage (COD) and gradual degradation due to optically accelerated facet oxidation. The main cause of COD is believed to be local heating due to optical absorption and non-radiative recombination of optically generated carriers at the facets, and the resulting positive feedback. Furthermore, the dielectric facet coating itself or the impurities in the coating can react with the semiconductor laser facets in the presence of light, heat and bias energies, resulting in facet degradation.
It is known that laser performance degradation can be reduced by provision of a contamination-free facet, followed by in-situ application of a passivation layer. U.S. Pat. Nos. 5,063,173 and 5,144,634 disclose that the passivation layer consists of Si, Ge or Sb, and that the passivation layer is deposited in situ onto a contamination-free laser facet. U.S. Pat. No. 5,171,717 discloses apparatus for cleaving semiconductor wafers in a vacuum system. See also U.S. patent application 08/408,678, filed Mar. 22, 1995 by M. Hong et al., which discloses gallium oxide as a passivation layer.
Despite the substantial progress that has been made, it would be highly desirable to have available lasers with a readily deposited facet passivation layers that can have further improved reliability. This application discloses such lasers, and a method of making the lasers.